I did a bit of taxidermy as a teenager including one small crab for a friend of my sister. I used the technique described in the book "Taxidermy" by John Metcalf:
Detach limbs from body.
Remove all flesh from limbs with with hooked wires.
Remove flesh from main body.
Wash evrything well in running water.
Immerse in 2% formalin solution for 2 to 3 hours.
Remove from formalin and wash thoroughly.
Paint inside with glycerine preservative solution (2/3 glycerine and 1/3 pure phenol)
Cut soft galvanised wires to fit into each limb.
Fill the body and limbs with modelling compound and position the limbs as required.
Support the specimen as needed and allow it to dry.
Detach limbs from body.
Remove all flesh from limbs with with hooked wires.
Remove flesh from main body.
Wash evrything well in running water.
Immerse in 2% formalin solution for 2 to 3 hours.
Remove from formalin and wash thoroughly.
Paint inside with glycerine preservative solution (2/3 glycerine and 1/3 pure phenol)
Cut soft galvanised wires to fit into each limb.
Fill the body and limbs with modelling compound and position the limbs as required.
Support the specimen as needed and allow it to dry.